This filter should be configured with the name envoy.grpc_http1_bridge.

This is a simple filter which enables the bridging of an HTTP/1.1 client which does not support
response trailers to a compliant gRPC server. It works by doing the following:

When a request is sent, the filter sees if the connection is HTTP/1.1 and the request content type
is application/grpc.

If so, when the response is received, the filter buffers it and waits for trailers and then checks the
grpc-status code. If it is not zero, the filter switches the HTTP response code to 503. It also copies
the grpc-status and grpc-message trailers into the response headers so that the client can look
at them if it wishes.

The client should send HTTP/1.1 requests that translate to the following pseudo headers:

:method: POST

:path: <gRPC-METHOD-NAME>

content-type: application/grpc

The body should be the serialized grpc body which is:

1 byte of zero (not compressed).

network order 4 bytes of proto message length.

serialized proto message.

Because this scheme must buffer the response to look for the grpc-status trailer it will only
work with unary gRPC APIs.

This filter also collects stats for all gRPC requests that transit, even if those requests are
normal gRPC requests over HTTP/2.